Where Do Black Day Dates Come From
Many people flip open the Chinese almanac, see the words "Black Day" (hei dao ri), and immediately skip past them — but very few ever look into where that label actually comes from. Black Day dates originate from the "Twelve Cycle" (Shi Er Zhi) system. The twelve positions are: Jian, Chu, Man, Ping, Ding, Zhi, Po, Wei, Cheng, Shou, Kai, and Bi, arranged in a continuous rotation with one position assigned to each day. The positions classified as Black Days are: Jian, Po, Ping, Shou, Bi, and Wei — six in total. The remaining six are called Yellow Day (huang dao ri) dates.
The logic behind this system is not mystical resonance but rather a mechanical rotation based on the day's Heavenly Stems and Earthly Branches — similar to how solar terms are calculated, cycling through all twelve positions before starting again. The "Jian" day in the almanac is also known as "Jian Chu" (jian chu), and historical commentators have not agreed on its auspiciousness. The "Xie Ji Bian Fang Shu" (Compendium of Auspicious Timing and Directions) explicitly states that "Jian" originally means "building strength" (jian wang), not pure misfortune — it is simply unsuitable for breaking ground or traveling, while being appropriate for ritual offerings. In other words, even within traditional texts, Black Day dates are contested rather than uniformly condemned.
The "Wei" day is the most interesting case. Literally it looks ominous, yet the "Xuan Ze Zong Jing" (Mirror of Date Selection) contains a view that Wei days are actually suitable for "travel and long journeys," on the grounds that Wei carries the meaning of "ascending heights and facing danger without coming to harm." This self-contradicting interpretation reveals that the Twelve Cycle system accumulated layers of commentary from different eras as it was transmitted, and different date-selection manuals were never fully consistent with one another to begin with.
Inauspicious Deities and Black Day Dates Are Two Different Things
Many people conflate these two concepts, but their origins are entirely different.
Black Day dates come from the Twelve Cycle system — they belong to the "day deity" (ri shen) framework and are calculated on a fixed periodic basis. Inauspicious deities, by contrast, are determined by combining the traveler's BaZi (Four Pillars of Destiny), the direction of travel, and the sha (malevolent energy) positions active in the current Annual Fortune — they carry a strong personal dimension.
Common inauspicious deities relevant to travel include:
- Sui Sha (Year Malevolence): A directional malevolent deity on duty for the year — in the year of Geng Zi it sits in the north, in Xin Chou it sits in the east, and so on.
- Five Yellow (Wu Huang): When the Five Yellow of the Xuan Kong Flying Star enters the central palace, the directions it visits are all unfavorable for movement.
- Yue Po (Month Break): The day that directly clashes with Tai Sui for a given month; folk tradition holds that setting out on a long journey on this day invites obstruction.
- Jie Sha and Zai Sha (Calamity Malevolences): Clashing with the traveler's year branch; tradition holds these preside over unexpected incidents.
Sui Sha and the Five Yellow are two factors that traditional date-selection practitioners tend to take seriously, because they come with directional references — allowing one to "move toward the auspicious and avoid the ominous." For instance, if Sui Sha sits in the east for a journey heading east, the traveler can reroute southward to sidestep it. Black Day dates offer no directional adjustment — the only remedy is to change the date entirely. This is the most practical operational difference between the two systems.
How People Actually Make the Call in Practice
A genuine date-selection practitioner will not pronounce a judgment based on Black Day dates alone.
The typical working logic goes like this: first eliminate Yue Po days — this step carries essentially no controversy, as tradition is unanimous that Yue Po days are unsuitable for major undertakings; then check whether the day falls on a "Wang Wang" (wang wang) — Wang Wang is an inauspicious day specifically targeting travel, derived from the year's Heavenly Stems and Earthly Branches, four days per year, and virtually all historical texts advise avoidance when traveling; only after both of those are cleared does one look at Black Day dates, which at that point serve only as a secondary reference.
Conversely, if a given day is a Yellow Day but simultaneously carries "Tian Zei" (Heaven Thief, tian zei) or "Gou Jiao" (Hook and Tangle, gou jiao), folk practitioners will discount it. Tian Zei days are traditionally associated with a higher risk of theft, and many people will reschedule a long trip if they encounter this designation.
One point worth clarifying: the auspicious and inauspicious entries in the Chinese almanac derive from different systems across different eras, and were typically stacked on top of one another during printing without any editorial filtering. It is very common for the same day to be simultaneously marked "suitable for travel" and flagged with an inauspicious deity. When an ordinary reader encounters such contradictions, they have no framework for resolution and tend to see only what they want to see — this is in fact the almanac's greatest practical problem.
Professional date-selection practitioners handle this through the principle of "weigh the heavy, ignore the light" (lun zhong bu lun qing): Yue Po, Wang Wang, and Sui Sha-class deities carry high weight; Black Day dates from the Twelve Cycle carry low weight. When the two conflict, the former takes precedence.
Some Often-Overlooked Details
Travel date selection also has a very concrete dimension: the hour of departure. Folk tradition holds that even with a well-chosen date, an inauspicious hour for setting out can still bring misfortune. This idea has some grounding: the Xing Chong (clashing) relationship between the day pillar and the hour pillar is examined independently in traditional fate analysis. For example, departing on a Zi (rat) day during the Chou (ox) hour — Zi and Chou form a He (combination) — is generally considered unproblematic; but departing on a Wu (horse) day during the Zi (rat) hour — Zi and Wu are in Chong (direct clash) — is traditionally discouraged.
Another detail is the direction of travel. Traditional practice holds that one should "travel toward the direction of one's Gui Ren (Noble Person)" (qu gui ren fang xiang). The Noble Person direction is determined by the day's Heavenly Stem: for Jia, Wu, or Geng days the Noble Person sits in the Chou or Wei directions; for Yi or Ji days in the Zi or Shen directions, and so on. Not every date-selection system emphasizes this, but it is preserved fairly intact in folk travel customs, particularly in southern China.
In practice today, most people simply check the almanac app on their phone and glance at the "suitable" and "unsuitable" column. The problem with that approach is that the calculation quality of phone almanac apps varies considerably — some even produce errors in their Twelve Cycle assignments. For routine short trips, a general sense of the day is probably sufficient; for choosing a date for long-distance travel or for matters requiring special consideration, it is better to consult a clearly sourced reference text or ask someone who can work through each factor properly.
Articles in this column are for cultural and educational purposes only and do not constitute life advice.